Artefactual punctate <scp>MLH</scp>1 staining can lead to erroneous reporting of isolated <scp>PMS</scp>2 loss

Hammond, Rory F.L.; Leen, Sarah Lam Shang; Faruqi, Asma; Trevisan, Giorgia; Gilks, C. Blake; Singh, Naveena

doi:10.1111/his.13663

Cited by 13 publications

(9 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…M1-clone had been used for all of these cases. Similar to our cases, all of them showed complete negativity on repeating MLH1-IHC with ES05-clone, and MLH1 promotor was methylated [11]. Loughrey et al reported a similar aberrant MLH1-IHC pattern with the M1-clone, in 9 of the 16 PMS2-negative CRCs from his cohort, and 4 of these showed somatic BRAF V600E mutation [12].…”

Section: Discussionsupporting

confidence: 87%

See 1 more Smart Citation

Granular dot-like staining with MLH1 immunohistochemistry is a clone-dependent artefact

Dasgupta

Ewing-Graham

Groenendijk

et al. 2020

Pathology - Research and Practice

View full text Add to dashboard Cite

Immunohistochemistry (IHC) for DNA mismatch repair proteins MLH1, PMS2, MSH2, and MSH6 is used for microsatellite instability (MSI) screening in colorectal carcinoma (CRC) and endometrial carcinoma (EC). Loss of PMS2, with retained MLH1 staining occurs in germline mutations of PMS2 gene, and is an indication for genetic testing. We report a pitfall of immunohistochemical interpretation in an EC, initially regarded as MLH1-positive and PMS2-negative. Review of the MLH1-IHC (M1-clone) revealed a granular, dot-like, nuclear staining. On repeating the MLH1-IHC with a different clone (ES05-clone), complete negativity was noted, and on molecular testing, MLH1 promotor methylation was detected. The dot-like pattern was therefore adjudged a clone-dependent artefact. On reviewing the archived MLH1-IHC slides, we observed the same dot-like pattern in two CRCs; in both cases the M1-clone had been used. Awareness of this artefact may prevent reporting errors, and unnecessary referrals for germline mutation testing.

show abstract

Section: Discussionsupporting

confidence: 87%

“…Niu et al recently reported a heterogeneous punctate nuclear staining with MLH1-IHC in 6 ECs, which had been originally reported as isolated PMS2-negative [11]. M1-clone had been used for all of these cases.…”

Section: Discussionmentioning

confidence: 99%

Granular dot-like staining with MLH1 immunohistochemistry is a clone-dependent artefact

Dasgupta

Ewing-Graham

Groenendijk

et al. 2020

Pathology - Research and Practice

View full text Add to dashboard Cite

show abstract

“…al. 2018; Loughrey et al 2019; Dasgupta et al 2019;Zhang et al 2020), and this has been noted to be more obvious in biopsy specimens rather than large resection specimens, as underlined by our contribution(Niu et al 2018, Zhang et al 2020. Punctate expression of MLH1 has been observed and reported for a speci c clone (the M1 clone, Ventana Medical Systems, Roche Diagnostics Division, Hofman La Roche Ltd, Basel, Switzerland), which was also used in our study, and it could represent either an increased sensitivity of the clone (which may recognize functionally impaired we have shown that, by decreasing primary antibody incubation times for biopsy samples, this greatly reduces spurious MLH1 expression.…”

supporting

confidence: 73%

Evaluating Mismatch Repair Deficiency in Colorectal Cancer Biopsy Specimens

Grillo

Paudice

Gambella

et al. 2023

Preprint

View full text Add to dashboard Cite

Mismatch repair (MMR) testing on all new cases of colorectal cancer (CRC), has for now been preferably performed on surgical specimens as more tissue is available, however, new clinical trials for the use of immune check-point inhibitors in the neoadjuvant setting require MMR testing on biopsy samples. This study aims at identifying advantages, disadvantages and any potential pitfalls in MMR evaluation on biopsy tissue and how to cope with them. The study is prospective-retrospective, recruiting 141 biopsies (86 proficient (p)MMR and 55 deficient (d)MMR) and 97 paired surgical specimens (48 pMMR and 49 dMMR). In biopsy specimens, a high number of indeterminate stains was observed, in particular for MLH1 (31 cases – 56.4%). The main reasons were a punctate nuclear expression of MLH1, enhanced MLH1 nuclear expression compared to internal controls or both (making MLH1 loss difficult to interpret), which can be solved by reducing primary incubation times for MLH1. Cases with adequate immunostains have a mean number of > 5 biopsies compared to ≤ 3 biopsies in inadequate cases. Conversely, surgical specimens rarely suffer from indeterminate reactions while weaker staining intensity (p < 0.007) for MLH1 and PMS2, and increased grade of patchiness (p < 0.0001) was seen. Central artefacts were almost exclusive to surgical specimens. MMR status classification was possible in 92/97 matched biopsy/resection specimen cases, and all of these were concordant (47 pMMR and 45 dMMR). Evaluation of MMR status on CRC biopsy samples is feasible and correlation between biopsy and surgical samples is excellent, if pitfalls in interpretation are known.

show abstract

“…Niu et al . have demonstrated, albeit in small numbers, an association in endometrial cancer of punctate MLH1 staining with MLH1 promoter hypermethylation . While most cases of CRC with loss of PMS2 staining and punctate staining of MLH1 also probably represent somatic hypermethylation of the MLH1 promoter, supported by the clinicopathological features of the patients in our series, we cannot exclude that this pattern may also be encountered in occasional Lynch syndrome‐associated cancers.…”

mentioning

confidence: 51%

“…Sir : We read with interest the description by Niu et al . of punctate immunostaining for the mismatch repair (MMR) protein MLH1 in a small series of cases of endometrial cancer, in association with complete loss of PMS2 immunostaining . The authors conclude that unawareness of this rare pattern of aberrant MLH1 staining can result in erroneous reporting of such cases as isolated loss of PMS2 staining, interpreted as probably representing Lynch syndrome due to germline mutation, whereas, in fact, somatic hypermethylation of the MLH1 promoter is the probable underlying molecular mechanism leading to defective mismatch repair in most such cases.…”

mentioning

confidence: 94%